1. Field of the Invention
This invention relates to door operators for doors on transit vehicles such as buses and trains. Some vehicle doors have a single panel mounted at an outside edge of the door opening. Many vehicle doors have two panels, each mounted at an outside edge of the door opening. The panels usually swing outward to permit entrance or exit of passengers. Often, the doors are caused to open or close with a pneumatic cylinder or electric motor and a well-known teeter assembly mounted over the top of the door opening. The space available for mounting the door operator over the door opening is often limited. Automatic opening and closing of the doors is controlled by the vehicle driver at stops for picking up and discharging passengers. It is an essential feature of door operators that the doors cannot be pushed open by passengers leaning against the doors, for example, while the vehicle is moving. However, in an emergency there must be a manual release that can be operated by a passenger. Generally, passengers must be able to operate the manual release with no more than 20 pounds pull force.
2. Description of Related Art
U.S. Pat. No. 5,332,279 entitled “Power Door Operator for Multi-Passenger Mass Transit Vehicles” discloses an electric door operator and illustrates the manner in which the spaced doors are rotated open and closed by the action of the teeter assembly connected to drive rods and pivot levers fixed to the vertical door shafts on which the doors are mounted. (See FIG. 1.)
U.S. Pat. No. 8,484,892 entitled “Electric Door Operator” discloses an electric door operator having a teeter 34 mounted on an output shaft 36. The teeter 34 has a drive arm 35 mounted to the output shaft 36 with journals at one or both ends for receiving drive rods. The teeter can rotate both clockwise and counterclockwise to operate the drive rods. Mounted on opposite sides of the housing are an electric motor 42 and an electric brake 44 connected to each end of an input (motor) shaft 46. The electric motor can be controlled to rotate either clockwise or counterclockwise. (See FIG. 2.)
The electric motor is coupled to the input shaft at one end and to the electric brake mounted to the input shaft, for example, at the other end. The electric brake is spring biased in the braking position with an electric release. An electromagnetic coil inside the electric brake releases a spring actuation such that when no electric power is available, the motor shaft is locked in position. Thus, a passenger leaning on a door will not force it open. Electric power is only required to open or close the doors and not to maintain the doors closed, Other fail safe braking systems can be used.
Mounted on the input shaft is a worm. A gear shaft is mounted rotatably, and preferably, perpendicular to the input shaft. A worm gear is fixed to the gear shaft in a position to engage the worm. A gear train connects the gear shaft to the teeter shaft. Within the gear train, a pinion has a sliding connection enabling axial movement between engaged and disengaged positions.
A manual release shaft is rotatable perpendicular to the housing. Rotation of the manual release shaft moves a cam mechanism that affects the movement of the sliding pinion. This arrangement allows for the emergency release of the input (motor) shaft from the teeter shaft permitting manual opening of the door in an emergency. The manual release shaft is spring biased in the engaged position.
An engagement/disengagement cam secured to the manual release shaft has spaced engagement cam surface portions and disengagement cam surface portions. An electrically operated actuator, for example, a solenoid, is fixed to the housing for pulling a spring biased stop away from the disengagement cam such that with the rotation of the manual release shaft the engagement/disengagement cam allows the spring biased stop to enter the disengagement cam surface portion preventing return of the sliding pinion to the engaged position until the solenoid is activated. Typically, actuation of the solenoid is only controlled by the vehicle operator.
In order to return the transit doors to an operational state, the solenoid is used to retract the stop to allow the manual release shaft to rotate back to the operational position. Such rotation of the lever is accomplished by a torsion spring around the manual release shaft urging the sliding pinion to the engagement position.
The primary disadvantage of this system is that the disengagement lever is only configured to accept a single mechanical input. Secondarily, the use of sheathed cables for the mechanical input imposes practical limits on the positioning of the disengagement lever. Applicant's invention overcomes these limitations by incorporating additional linkage enabling additional inputs without interfering with a primary release cable.